Search for pair production of additional neutral scalars within the Inert Doublet Model in a final state with two electrons or two muons in proton-proton collisions at $\sqrt{s}$ = 13 TeV and 13.6 TeV

TL;DR

This paper reports a search for new scalar particles predicted by the Inert Doublet Model in proton-proton collisions, using neural networks to distinguish potential signals from background, but finds no significant excess.

Contribution

First dedicated search for pair production of Inert Doublet Model scalars using neural networks and LHC data, setting new exclusion limits on their masses.

Findings

No significant excess observed in data.

Exclusion limits set up to 108 GeV for H mass.

Parameter space coverage extends previous bounds.

Abstract

A first dedicated search for pair production of new scalars predicted by the Inert Doublet Model is performed using proton-proton collisions. Data were collected with the CMS detector at the CERN LHC at $\sqrt{s}$ = 13 TeV and 13.6 TeV, corresponding to integrated luminosities of 138 fb$^{-1}$ and 35 fb$^{-1}$, respectively. Within this model, four additional scalar bosons (H, A, H$^+$, and H$^-$) are predicted. Through an additional discrete symmetry, the lightest new scalar, H, is stable, rendering it a viable dark matter candidate. These candidates can originate from quark-antiquark annihilation producing an offshell Z boson that decays to a pair of the new scalars. The target final state consists of exactly two opposite-charge same-flavour leptons (electrons or muons), with missing transverse momentum due to the stable neutral scalars, and very little hadronic activity. A parameterised neural network is used to separate the signal from the standard model background. No significant excess of events is observed. Exclusion limits at 95% confidence level are set on the production cross section of the two new neutral scalars, H and A, expressed in terms of their masses, $m_\mathrm{H}$ and $m_\mathrm{A}$, in the $m_\mathrm{H}$ vs. $m_\mathrm{A}$ plane. The observed (expected) exclusion region reaches $m_\mathrm{H}$ = 108 (106) GeV for $m_\mathrm{H}-m_\mathrm{A}$ = 78 (76) GeV and at $m_\mathrm{H}$ = 70 GeV, covers the range of $m_\mathrm{H}-m_\mathrm{A}$ = 40$-$90 (35$-$90) GeV.